E34 Failing Smog, Running Rich, Any others with this and any solutions?

[kouks]

The full story of this smog certification saga is on this thread:

http://forums.bimmerforums.com/forum/showthread.php?1982813-Possible-MAF-problem&highlight=MAF

But, now after I did all that maintenance, it tested worse than before. Yesterday I installed replcement cats from a salvage e34. These are aftermarket cats. The smell of the exhaust has changed, maybe for the better, but it still smells like fuel, so I'm still running rich.

If you don't want to read the other thread, here are some cliff notes:

1. Smog Test #1: Passed 15 mpg, Failed 25 mph smog test for HC and NO, about 50% higher than allowed.
2. Replaced O2 sensor, replaced ECU temp sensor, replaced MAF (salvage), new NGK spark plugs, replaced intake manifold gaskets, replaced throttle body gaskets, cleaned TB and intake, cleaned ICV, inspected all vacuum hoses for cracks, breaks, etc.
3. Smog test redo: Failed both 15 and 25 mph, both on HC and NO, and at almost double allowed.
4. Replaced original with aftermarket salvage cats. No new smog test yet.

So the question is, what drives the ECU to command such a rich condition? Have any others ran into a rich running condition and what have you done to solve it? Any ideas would be appreciated.

Car is 1995 525i, M50 motor, 239,000 miles, original owner for 17.5 years. Please help me save a family friend.

[TheStigg]

Have you tried a "Shogun reset" (disconnect the battery)? Do another oil change with a heavier weight & drive it like you stole it for 1/2 hr afterwards, redline is your friend. Go immediately to the smog station for a re-test while it's good and hot. If it still fails, could be the donor cats weren't that good.

I drove the piss out of my wife's e36 M50 & it passed emissions but failed the gas cap pressure test. I didn't realize that while hot-footing it on the way to the emissions test, it spun the impeller on the waterpump shaft, and overheated on the way home to get a spare cap & threw the temp sensor code. I replaced the waterpump, thermostat, temp sensor, & plugs & it failed emissions the 2nd time. Did a Shogun reset & it passed easily the 3rd time. Apparently the 2nd time, the ECU "remembered" the overheat/temp sensor failure and it went open loop.

[kouks]

Apparently the 2nd time, the ECU "remembered" the overheat/temp sensor failure and it went open loop.

Funny you should mention that. When my wife went in for a retest a week ago, I had just replaced some of the heater hoses while I was re-doing the manifold. Apparently I forgot to tighten one of them and it popped off and overheated during the test. Messed up the smog test facility good too. I'll give that a shot too. This retest will cost $30, hopefully the donor cats will do a better job.

[Korath]

There was a suggestion on the MPG thread about discharging the ECU using the chassis ground and positive terminal of the harness; a slightly more effective reset if you will. You just have to drive until it reads as being ready.

[TheStigg]

Ouch! That would be a hard short passing many 10's of Amps? Surely you mean with the battery disconnected.

[Binjammin]

Ouch! That would be a hard short passing many 10's of Amps? Surely you mean with the battery disconnected.

Positive terminal of the harness. Not the positive terminal of the battery. There should be no voltage if the positive terminal of the harness is disconnected from the battery.

[kouks]

Positive terminal of the harness. Not the positive terminal of the battery. There should be no voltage if the positive terminal of the harness is disconnected from the battery.

Ive read of this before on the e38 forum where that darn thing has plenty of battery issues. I'm off work tomorrow so I'll do it then.

[ShapeShifter]

Capacitive discharge....

[TheStigg]

Positive terminal of the harness. Not the positive terminal of the battery. There should be no voltage if the positive terminal of the harness is disconnected from the battery.

Short it initially thru a 1k-ohm resistor, then do a dead short.

[Grim Reaper]

Your car probably has one or more weak/failed coils. Also, it is not your cats. Any properly tuned car can pass smog without cats.

[Binjammin]

Short it initially thru a 1k-ohm resistor, then do a dead short.


Why? You're not feeding anything into it, and the only load on it is to drain whatever is in there... it's not like you've got a continual low voltage load to mess anything up...

[TheStigg]

Why? You're not feeding anything into it, and the only load on it is to drain whatever is in there... it's not like you've got a continual low voltage load to mess anything up...

There's a non-trivial amount of stored energy in the 100's of caps in the dozens of components and IC circuits throughout the vehicle. Shorting through a resistor will clamp the resulting voltage spikes when shorting, and drain the discharge current at a safe level. You've probably observed a slight spark when doing a hard short of the disconnected positive battery cable to ground. The stored energy does bleed off over time if not shorted. Doing an immediate hard short without a resistor will produce high transient currents for the first few quarter cycles, which could have adverse effects.

[kouks]

Your car probably has one or more weak/failed coils. Also, it is not your cats. Any properly tuned car can pass smog without cats.

What I'm wondering is if the valve seals or rings are starting to go since it started to burn oil about a year ago. However the plugs were clean when I pulled them. Ill be doing a compression test and if I can get my hands on a compressor a leak down check too.

[kouks]

Grounded the pos and neg, checked resistance on the coils and coil harness and they were good.

[mgoods50]

Coils can't be checked with that- you're only measuring primary. To properly test you need an oscilloscope. I feel like I've stated this a million times lately- so sorry if anyone recognizes the frequency. Still true though!

m6x can be a pain. If you aren't misfiring (and it's hard to tell on that engine sometimes)-- wait, you're OBDII- you should have codes if that's the case... anyway, if you aren't misfiring- get the cats nice and cooking- that's your best friend for emissions. What plugs are you running? Swap in some plain old copper plugs- trust me.

IF we can get you through smog, we can work on the rest later :)

[kouks]

Coils can't be checked with that- you're only measuring primary. To properly test you need an oscilloscope. I feel like I've stated this a million times lately- so sorry if anyone recognizes the frequency. Still true though!

m6x can be a pain. If you aren't misfiring (and it's hard to tell on that engine sometimes)-- wait, you're OBDII- you should have codes if that's the case... anyway, if you aren't misfiring- get the cats nice and cooking- that's your best friend for emissions. What plugs are you running? Swap in some plain old copper plugs- trust me.

IF we can get you through smog, we can work on the rest later :)

Thanks man, I'm testing it again today after the donor cats have been in and running a couple days. Hopefully they do the job. Plugs are new copper NGK with two prongs.

I'm actually OBD1, and no codes. The engine runs great. At idle with the hood closed you could barely hear it, with the hood open all you hear is a slight VANOS rattle. The only performance issue I have is that when I floor it it does not spring alive any more under load, It does not hesitate but the power comes in slowly and takes about 2 seconds to really rev up. In the driveway under no load it revs up much better. Not that the M50 is a powerhouse motor, but it was more lively than it is now.

[locknload]

Checked TPS?

[kouks]

Checked TPS?

Hmmm. No. I also just read (Bentley manual) not to spray carb cleaner in the TB since it can damage the TPS. You're supposed to spray a rag and wipe it down that way. Wish I read that earlier.

[mgoods50]

Sorry- I'm running about 4 degrees retarded lately...

I just did a little instructional on checking the TPS, in case you're not familiar, or don't remember off hand.

I've cleaned a lot of TB's without removing the TPS-- maybe just luck I haven't damaged them!

Plugs are the ones that basically have no complaints- so you should be good there.

[kouks]

PASSED!

Although the guys looked at my past numbers then took the car for a drive. I got nervous when they were gone for 20 minutes, but they put it on the machine and it passed. Maybe the newer cats helped.

Good for two more years, but I'm still going to keep digging until I find the culprit. Also did a compression check warm and no problems noted. As expected, the M50 is still strong.

Do you have a link on the TPS check?

[Grim Reaper]

This is just to help you understand your issue...

You have a lean burn problem. You are not running rich by your numbers. You have to realize that a misfire / incomplete combustion accounts for your high HC and then the DME recognizes that condition and then leans out the mix and as that is averaged out across all 6 cylinders you tend to get high combustion temps and the result is more NO in the 5 or so cylinders that are probably running/firing ok.

[kouks]

^This may be the answer. I was told the engine is running hot, but the coolant temp looks normal. If all the plugs are good and compression is good, then ill need to run a leak down check to find any valve issues and if not then try to find the bad coil. Thanks for the input.

[mgoods50]

PASSED! . . .Do you have a link on the TPS check?

Viola! http://forums.bimmerforums.com/forum/showthread.php?1988432-TPS-testing-via-DMM

Glad you passed!